From b9ddea7cd00a0b31446bf6c235d3ada2feab8c13 Mon Sep 17 00:00:00 2001
From: Herr Frei <herr.frei@gmail.com>
Date: Mon, 7 Sep 2026 13:50:40 +0200
Subject: [PATCH] Save system time to RTC on shutdown
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**Problem:**
Currently, `tc-config` reads the RTC on boot, but `rc.shutdown` never writes the system time back to the RTC on shutdown. As a result, any time drift or NTP-based correction made during the session is lost, and the hardware clock gradually becomes stale across reboots.

**Fix:**
Added a step in `etc/init.d/rc.shutdown` that writes the current system time back to the RTC via `hwclock -w`, mirroring the boot-time logic in `tc-config`:

- Respects the `nortc` boot code — RTC write is skipped entirely if RTC handling was disabled at boot.
- Respects the `noutc` boot code — uses `hwclock -l -w` (local time) if set, otherwise `hwclock -u -w` (UTC), consistent with how the clock was read at boot.
---
 etc/init.d/rc.shutdown | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/etc/init.d/rc.shutdown b/etc/init.d/rc.shutdown
index ff96e21..de0bd26 100755
--- a/etc/init.d/rc.shutdown
+++ b/etc/init.d/rc.shutdown
@@ -14,6 +14,17 @@ if ! grep -q "noswap" /proc/cmdline; then
    swapoff -a 2>/dev/null
 fi
 
+# Save system time back to the Hardware Clock (RTC), unless disabled
+# via boot code. Mirrors the logic used in tc-config at boot time.
+if ! grep -q "nortc" /proc/cmdline; then
+   echo "${BLUE}Saving system time to Hardware Clock (RTC).${NORMAL}"
+   if grep -q "noutc" /proc/cmdline; then
+      /sbin/hwclock -l -w 2>/dev/null
+   else
+      /sbin/hwclock -u -w 2>/dev/null
+   fi
+fi
+
 # Kill all processes except those listed in /var/tmp/k5_skip.
 K5_SKIP=$(awk 'BEGIN {RS="[\n ]";ORS=" "}{print "-o "$1}' /var/tmp/k5_skip)
 echo "${RED}Killing $K5_SKIP all processes."